The following procedure (RRC CONNECTION REJECT with redirection) has been known as a procedure for a mobile communication terminal (UE) to establish a connection from a first communication system (first RAT (Radio Access Technology)) to a second communication system (second RAT) in a mobile communication system (for example, non-patent document 1).
First, the mobile communication terminal transmits to the first communication system a radio signal (RRC CONNECTION REQUEST) in which information (pre-redirection info) indicating capability to support the second communication system is set.
Secondly, in response to the radio signal (RRC CONNECTION REQUEST) from the mobile communication terminal, the first communication system transmits a radio signal (RRC CONNECTION REJECT) to instruct the mobile communication terminal to connect to the second communication system (redirection).